comes on a day when president obama redefined america's war on terror. He delivered a major speaks, causing fireworks right there in the room. Here's abc's chief white house correspondent, jonathan karl. Reporter: It's a secret war. Unmanned aircraft operated out of nondescript rooms, tracking suspected terrorists, firing on tahalf a world away. Not a video game. This is deadly. By most estimates, killing more than 2,000 people since barack obama became president. Under criticism that this is a secret war with no accountability, the president now wants to take it out of the shadows, and is calling for new limits. Even saying, the war on terror must eventually end. This war, like all wars, must end. That's what history advises. That's what our democracy demands. Reporter: In the meantime, strict rules on the use of drones. Now only to be used on targets podsing an imminent and ongoing threat to the u.S., And only whether there is near certainty that no civilians will be hurt or killed -- and they are never to be used to punish terrorists for past attacks. As for the controversial targeting of american citizens turned terrorists -- I do not believe it would be constitutional for the government to target and kill any u.S. Citizen with a drone or with a shot gun, without due process. Reporter: The president once again made the case for closing the prison at guantanamo bay. At one point an anti-war protester tried to shout him down. Why was he killed? Ma'am, part of free speech is you being able to speech, but also you listening and me being able to speak. Reporter: She interrupted him three separate times. I'm willing tout can the young lady who interrupted me some slack because it's worth being passionate about. Jon karl joins us from the white house. The president has been talking about closing get mo for years now. What are the odds he can get it done this time? Reporter: He's going to renew the effort to get some of them back to their home countries. He talked about the costs. 160 detainees in guantanamo bay, a million dollars a year to keep them there. He'll try to appeal to some republicans by saying it's just too expensive. Thank you. Now to big news across the

This transcript has been automatically generated and may not be 100% accurate.

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